The present invention relates to a digital mark-printer, and more particularly relates to a printer controlled by stored program within a microprocessor system and that automatically and programmably performs the function of printing a variety of marks, such as postmarks used in the postal office.
Similar printing functions are disclosed in U.S. Pat. No. 3,965,815, wherein a mechanism for sequentially setting the print wheels in a postage printing device is described. The setting mechanism is electrically controlled to interface the postage printing device with a computerized or electronic postage system. The setting mechanism comprises a main rotatable driving gear which is slidable upon a splined shaft so as to individually, operatively engage a plurality of print wheel driving racks in a sequential fashion. A setting linkage connected to the main driving gear positions the gear into individual engagement with a plurality of rotatable shafts individually driving each of the print wheel driving racks. A stepper motor is connected to the splined shaft, which in turn rotatably drives the main drive gear. The setting linkage is actuated by means of a pair of solenoids.
However, such device has a drawback. Due to its inherent spatial limitation, only a single pair of solenoids 60, 70 can be arranged in the device which permits control of only four driving racks 43a, 43b, 43c and 43d, thus making only four marks available. However, there must be at least five changeable marks in a postmark in order to automate postmark printing, thus making this device impractical.